Which type of virtualization allows running multiple instances on a host OS without requiring a full guest operating system?

The ability to run multiple instances on a host operating system without the need for a complete guest operating system describes paravirtualization. This virtualization technique allows guest operating systems to communicate directly with the hypervisor, enabling them to run more efficiently than they would under full virtualization conditions.

In paravirtualization, the guest operating systems are modified to support the hypervisor, allowing them to know they are running in a virtualized environment. This leads to reduced overhead compared to full virtualization, which requires a more substantial emulation of hardware, resulting in running a full guest OS.

This makes paravirtualization particularly effective for performance-sensitive applications since it reduces overhead by sharing resources and enabling better interaction between the host and the guest systems. In contrast, other virtualization types, such as Type I and Type II hypervisors, either run directly on hardware or on top of an existing host OS without necessarily improving the interaction efficiency seen in paravirtualization.